Using in situ hybridization (ISH) and the polymerase chain reaction (PCR) we have recently detected the DNA of the Epstein-Barr Virus (EBV) selectively in proximal tubule (PT) epithelial cells of human renal biopsy material obtained from individuals with primary or "idiopathic" interstitial nephritis (IN). Drug related acute IN, primary glomerulopathies, renal vascular disease and acute tubular necrosis served as negative controls. These observations form the basis of the current research project in which we propose that EBV infection of renal PT cells plays a pivotal role in the initiation and/or progression of the inflammatory and injury pattern seen in "idiopathic" IN. This hypothesis will be evaluated by examining the following experimental aims: (I) To further examine the specificity of EBV DNA presence in renal biopsy material obtained from individuals with "idiopathic" interstitial nephritis vs other renal diseases; (II) To investigate whether proximal tubule (PT) epithelial cells selectively posses the CD21 cross-reacting antigen/C3d receptor and to explore whether this receptor mediates entry of EBV into the PT cell; (III) To determine whether infection of PT cells by EBV results in expression of virus-encoding neoantigens (lytic phase and/or latent phase) which may function as a target for cell-mediated immunity; (IV) To explore whether EBV infection plays a role in chronic interstitial inflammation associated with chronic rejection of the transplanted kidney. Renal biopsy specimens will constitute the major source of material In some protocols discarded human kidneys not suitable for transplantation or normal kidney tissue obtained from nephrectomy specimens procured during cancer surgery will be used for the preparation of isolated freshly prepared proximal tubule cells or the establishment of primary cultures. The latter will be used for gene transfer and in vitro infection experiments. The major methodologies to be employed include ISH, PCR, in situ PCR-lSH, immunoprecipitation, immunoblotting, immunohistochemistry and flow cytometry analysis. The information obtained from this research project will be synthesized into an integrated model that will provide new insights into the mechanisms of renal interstitial injury patterns and could lead to the development of effective therapies for a disease process which is an important cause of end stage renal failure.